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Sept. 11, 19 23. 1.467.843

w. M. DNN ET AL PROTEGTIVE SYSTEN Original Filed Sept. 10 19 15 INVENTORS Wa/fcr /II 0000 (hr/n Le6I Far/e501:

7 ATORNEY Patented Sept. 11, 1923.

UNITED STATES 1,467,843 PATENT OFFICE.

WALIER M. DANN, OF WILKINSBURG, AND CHARLES LE G. FORTESCUE, OIE PITIS- BURGH, PENNSYLVANA, ASSIGNORS T0 WES1INHOSE ELECIBIC AND MANU- FACIUBNG COMIANY, A CORPORATION OF PENNSYLVANIA.

PROTECIIVE SYSIEM.

Original application iiled September 10, 1915, Serial No.

50,112. Divided and this application flled November 11, 1918. Serial No. 331,493. -Rencwed October 17, 1919.

T0 all whom it may concem Be it known that we, WALIER M. DANN, a citizen of the United Statcs, and a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania, and CHARLES Ln G. Fomnscon, a subject of the King of England, and a resident of Pittsbur in the oounty of Allegheny and State of ennsylvania, have invented a new and useful Improvement in Protective Systems, of which the followin is a specification, this being a division 0 application, Serial No. 50,112, filed Sept. 10, 1915.

Oui invention relates to protective systems having special relation to systems which may be employed in connection with electrica1 apparatus to safeguard it from excessive tem eratures arising from the fiow therethmugx of abnorma1ly high currents on 0Velloads, and it has for its object to provide protective systems of the character designated which shall be instrumentai in conservin when not needed, the cooling means Whlch are employed bo neutralize the heating efiect of the aforesaid heavy currents.

More particularly, our invention relates to cooling means for electrica1 transformers and is particularly ada ted for employment with transformers whicli are immersed in an insulating fiuid containing coils of pipe through which cooling fluid is adapted to floW.

In transformers of the character designated, the present ractice is to allow water to pass through t e cooling coil in such quantities that the highest permissable temperature which the insulating fluid may mach, on account of heavy currents flowing through the transformer windings, is notexceeded. Such a system is of undoubted benefit where the transformer works on a steady load and the temperature fluctuations within the transformer tank are of :1 minimum amniunt. However, when large power transformrs, cooled in the above-mentioned manner, are utilized in railway systems or in other systems Where the power demands fluctnate over an extremely large range, it is essential that the cooling means-in this instance, the amount of water flowrng through the pipe coilshall be so governcd that only such amount of water shall pass through the coil as is required by the temperature of the insulating fluid.

In many installations, it is found that a saving of approximately in the amount of water used may be efiected by means of our invention, as compared with the usual practicc.

It is obvious, in large transformers, some of which have a Water rate of 9% gallons per minute, it is almost imperative that means shall be provided to save as much Water as possible, and this is es ecially truc where the water must be paid for by the gallon, as is the case in many localities.

Moreover, a number of the protective systems now in use in connection With transformers contemplate the opening of the load circuits of the transformer when a certain predetermined load current is exceeded. After the load circuits have been interrupted, many of the devices of the character designated will allow the transformer to cool and thereafter place them again in service by closure of the circuibintermpting means. Obviously, this method is open to many objections, the chief of which is the fact that the load circuit of the transformer is opened whenever the predetermined conditions are exceeded. It Would be a great saving if it were possible to keep the transformer in continuous service, aven under the heavyoverload conditions and to so arrange the protectiVe apparatus that an additional response of the cooling means would be had under the influence of the heavy-load currents.

ne object of our invention, therefore, is to arrange a protective system which is responsive to both the excessive currents flowing in the Ioad circuits and to the temporature of the surrounding fluid in which the electrical device is positioned. So far as we are aware, the idea of arranging a protective system, in this case a cooling system, in such manner that it will be influenced by both of the above elements, is novel and, thereforc, such a system might Well be employed with electrical apparatus which is used without insulating fluid but is surrounded by air since, as will hereinafr appear,a system constructed in acoordance With our invention could easily be adapted to operate to supply cooling fiuid directly to the electrical device itself as, for instance, a system wherein the cooling air supplied to an electrical apparatus is dependent upon both the load cnrrent and the temperature of the medinm surrounding th anparatus.

Moreover, as will hereinafter appear from the detailed description of our apparatus, the means which we have provided as responsive to both the load and the temperm tare conditions of an electrical device are constructed in such manner that the temperature of any portion of the electrical apparatus may be accurately reproduced in miniature, and, therefore, even if an electrical device develops abnormaily hot spots when supplied With heavy currents, provision may be made to cool such hot spots by s0 constructing the thermal responsive means that the conditions existing at the predetermined hot spots are accurately reproduced in the devioe which is instrumental in controlling the amount of the cooling means.

For a. better understanding of the nature and scope of our invention, reference may be had to the following description and the accompanying drawing in which Fig. 1 is a view, partially diagrammatic, partially in elevation and partially in section, of a transformer embodying a form of our invention, and Fig. 2 is a view showing a modified form of a portion of the apparatus shown in Fig. 1.

Referring to Fig. 1, et transformer 1 comprising a oore member 2, a bottom end frame 3 and spaced pancake coils 4 and 5, is disosed in a containing case 6. A body of msulating fluid 7, such as 011, is contained in the case 6 and completely immerses the transformer 1. Hgh-tension leads 8 project through a pair of outlet bushings 9 and lowtension leads 10 pr0ject through a pair of outlet bushings 11. A cooling coil 12, dis posed above the transformer 1 and submerged in the body of insulating fluid 7, is supplied with a cooling fluid through an in et pipe 13 which, in turn, is supplied through a. hand valve 14 and an automatically-actuated valve 15 that are inserted in the su ply lino intermediabe the inlet pipe 13 an a feed pump 16. A motor 17 is shown direrztly coupled to the feed pump 16 in order to provide for a continuous circulation of the cooling fluid through the cooling coil 12. By opening the hand valve 14, the cooling coil 12 is supplied with a constant flow of cooling liquid which, for ordinary operating conditions, is ade uate for cooliny; the transformer winding. %owever, when the transformer is subjected to excessive overloads or frequent peak loads which may cause hot spots of dangerously high temperatures to be developed in the transformer, it is essential to increase the flow of the eooling fluid throu h the cooling coil 12 in order to adequate y protect the transformer. To this end, We have provided the auxiliary by-pass valve 15, the operation of which is automatically effected by means of a temperature re ulator 18, Which, in turn, is influenced by t e temperature conditions obtaining in the hottest portion of the transformer 1. 7

The regulator 18 comprises a. thermostatic element 19 and a controller element 20. The thermostatic element comprises a tubular receptacle l9 containing a bod of heavy hydro-carbon oil and an expansi le and con tractible corrugated metal tube 20. The controller element 20 comprises a tubular member 22, the upper end of which is connected to the up er end of the tubular receptacle 19 by a tue 21 of small diameter. An expansible and contractible corrugad metal tube 23, capable of being compressed when an increase of temperature causes the liquid contained in the tubular receptacle 19' to expand, is contained within the tubular member 22. It Will be noted that the tubular receptacle 19, the tube 21 and the tubular member 22 constitute a hermetically closed chamber. When the temperature of the body of liquid contained in the tubnlar receptacle 19' increases, the pressure thus developed is transmitted to the tubular member 22 to effect compression of the corrugated tube 23. As a result, a piston 24 in the member 22 is actuated to operate an arm 25 which, in turn, actuates the by-pass valve 15. Under normal conditions, the desi of the structure is such that the bypass va ve 15 is kept closed.

The tubular receptacle 19" of the thermostatic element 19 is embraced by a heating coil 26 which is connected in circuit with the secondary Winding 27 of a. series transformer 28, the primary winding 29 thereof being connected in circuit with the secondary leads 10 of the transformer. The heating coil 26 is covered by a. suitable heat-insulafing material or lagging 30. It follows that the current flowing through the lieating coil 26 is proportional to the load-current traversin,q the windings of the transformer.

Those familiar with the design of transformera may accurately determine the temperature obtaining in any selected portion or the portion of a transformer in which the highest temperature will develop as a result of the unequal cooling facilities aflorded the various portions thereof. The data required for determining the temperatures of these se- ]ected portions, and particularly the hot spots in a transformer comprise the weight of the copper employe the watts to be dissipated per pound of copper, the exposed surfaces of the transformer coils, etc. From this data, the thermal capacity of the transformer may be determined and also the heat adient through the windings to the body ofoolin liquid or ail 7. As a conquence thereo the temperatures of the hottest portions of the transformer winding, under all conditions of load, may be accurately calculated. Thcrefore, by reproducing, in miniature, the temperature conditions obtaining in the hottest portion of a transformer and utilizing them to actuate the temperature regulator 18, the cooling of the transformer may be regulated in accordance with the instantaneous value of the temperature of the hottest portion of the winding, under all conditions of load. To accomplish this, the heating coil 26, in combination with the thermostatic clement 19, is so designed as to have the same heat emissivit y as the transformer 1 which, as above ment10ned, may be calculated from the data available to the designing engineers. The characteristics of the heat1ng coil 26 must be such that the percentage of copper par unit of volume is same as that of the transformer windings, the heat dissipabed per unit volume by the coil 26, under given load conditions, must be the same as that of the transformer windings, and the emissivity of the oil must likewise corres ond to that of the transformer windings. ince these various factors may be predetermined With substantial accuracy, as above mentioned, and made adjustable within certain limits by means of taps on the heating coil 26 and the lagging thereof, the temperature conditions obtainmg in the hottest portion of the tramsformer may be thus reproduced and utilizea to influence the action of the thermostatm element 19 of the temperature re ulator 18.

VVhile the valve 15 shown in ig. 1 o erates to supplement the flow of cooling fluid passing through the valve 14, it is possible to msert the valve 15 in the supply mains as to regulate the entire flow of the cooling fluid admitted to the cooling coil 12. This embodiment is shown in Fig. 2 in which the temperature regulator 18 operates the arm 20 of the valve 15 that constitutes the only regulating device for controlling the flow of the cooling fluid passing through the inlet pipe 13. The remaining structure shown in Fig. 2 is similar in all respects to that shown in Fig. 1, and the operation of the temper turc regulator 18 is likewise controlled by the heating coil 26, as explained in connecfion with Fig. 1.

Although we have shown and described our invention as applied to a specific structure, such as a power transformer, it is evi dent that it may be applied to many other types of apparatus and, therefore, since we consider the idea of arranging a thermal responsive device to be influenced both by the load current of the electrical device and by the temperature of the surrounding medium of said device to be entirely novel, we desire that the very broadest interpretation be placed upon the appended claims and that due consideration be given to the fact that various modifications therein may be made by those skilled in the art without involving a departure from the spirit and scope of our invention.

We claim as our invention:

1. The combination with an electrical device, and means for delivering a cooling medium thereto, of means influenced both by the load current of said device and by the temperacure thereof for governing the delivery rate of the cooling medium.

2. The combination with an electrical device, and means for delivering a cooling medium thereto, of means influenced both by the load current of said device and by the temperature thereof for automatically governing the delivery rate of the cooling medium and additional means for manually var ing the delivery rate of the cooling me mm.

3. The combination With an electrical device, a container therefor, fluid in said container in which said device is placed, and means for delivering a cooling medium thereto, of' means responsive to the load current of said device and to the temperature of said fluid for governing the delivery rate of said cooling medium.

4. The combination with an electrical device, a container therefor. fluid in said container in which said device is placed, and means immersed in said container, through which a cooling medium is passed, of means influenced both by the load current of said electrical device and by the temperature of said fluid for varying the amount of cooling fluid assing through said means.

5. he combinacion with an electrical device, a container therefor, fluid in said container in Which said device is placed, and means immersed in said container, through Which a cooling medium is passed, of means for reguIang the rate of flow of the cooling medium comprising a current coil energized in proportion to the load current of said device and immersed in said fluid, whereby it is aflected jointly by the load current and the temperature of the fluid.

6. The combination with an electrical device immersed in an insulating fluid, and a cooling coil for said insulating fluid, of means comprising, a current coil energized in proportion to the load current of said electrical device and immersed in said insulating fluid, means whereby the cooling fluid passing through said cooling coil may be varied to any desired degree,and actuating means associating said first means and said coolingcoil supply means, whereby the amount of said cooling fluid passing through said cooling coil is automatically varied in accordance with the load current of said device and in accordance with the temperature of said insulating fluid.

7. The combination with an electrical apparatus, of means infiuenoed by the load current of said apparatus and by the temperature thereof comprising heat-storage and heat-insulating materials, the ratio of the heat-storage capacity of said means to the heat-insulatin material thereof being the same as that 0 the heat-storage material to the heat-insulating material of the electrical apparatus.

8. In combination with an electrical apparatus comprising heat-insulating material, a protective device comprising a currentcarrying means traverser! by a current proportional to the current of said electrical apparatus and heat-insnlating means, the temperature of said protective device being influenced by that of said material and the ratio of the material of the currentcarrying means of said device to the heat-insulating material thereof being the same as the ratio of the corresponding portions of the electrical apparatus.

9. In combination with an electrical apparatus embodying 'currentcarrying material and heat-insulating material, a protective device comprising a current-carrying coil and heat-insulating material associated therewith, the temprature of said device being infiuenced by that of said heat-insulating material, the percentage of currentcarrying material par unit volume of the coil being the same as that of the current-carrying material of said electrical apparatus, and the heat dissipated per unit volume of the coil being the same as the heat dissipated per unit volume of the current-carrying n1aterial of said electrical apparatus.

10. In combination ith an eleetrical apparatus, protective means theref0r comprising a coil adapted to carry a current reportional to the current of said electrica apparatus and laggin material associated with said coil, the ratio of the heat-storag capacity of said coil to the lagging material thereof being the same as the ratio of the corresponding factors of the electrical apparatus to each other, and the protective means being disposed ILa medium which has the same temperature as that in Which the electrical apparatus is located.

11. The co1nbination with an electrical apparatus that is subjected to variable loads and heating conditions incident thereto, of a temperature-responsive device associad with said apparatus and influenced by the same cooling medium, said device comprising a current-carryin clament that is heated in accordance W1th the current traversin said electrical apparatus and is surroun ed by heat-insulating material, the relative proportions of heat-insnlating material and heat-generating material comprising the current-carrying element being so adjusted that the temperature characteristic of said device substantially corresponds, in time and form, to the temperature chamoteristic of said apparatus, irrespective of the variable load conditions that may be imposed thereupon.

12. The combination with an electrical apparatus subjected to the flow of a cooling medium and to variable loads and heatstorage conditions incident thereto, of a protective device associated with said apparatus and positioned to be influenced by the same cooling medium -possessing corresponding temperature conditions, said device comprising a current-carrying coil that is heated in accordance with the current traversing said electrical apparatus and lagging mate rial, the relative proportions of the heat storage material of said device and the lagging material thereof being so adjusted that the temperature characteristic of said device substantially corresponds, in time and form, to the temperature characteristic of said apparatus. irrespective of the variable loads imposed thereupon.

13. The combination with an electrical apparatus subjected to the fio of a cooling medium and to fluctuating loads, of a thermal protective device associated with said apparatus and influenced by a cooling medium having a temperature which substan tially corresponds to the temperature of the cooling medium for said apparatus, said device comprising a current-carrying coil traversed by a current that is roportional to the fluctuating loads impose upon said apparatus, and heat-insulating material, the ratio of' the heat-storage capacitv of said device to the heat-insulatm material thereof being the same as that 0 the heat-storage capacity to the heat-insulating material of the electrical apparatus, thereby imparting to said device a, temperature characteristic which substantially coincides, in time and form, to the temperatnre characteristic of said apparatns, irrespective of the fluctuating loads imposed upon said apparatus and the time of their duration.

In testimony whereof, we have hereunto subscribed our names this 8th day of Nov., 1918.

WALTER M. DANN. CHARLES LE G. FORTESCUE. 

